The present invention relates to a technology of controlling an internal combustion engine of a hybrid powered vehicle including two driving sources, i.e., an internal combustion engine and an electric motor.
In recent years, what has been requested of an automobile etc is to reduce a burned fuel quantity of an internal combustion engine and to purify an exhaust gas discharged from the internal combustion engine. In response to these requests, there has been developed a hybrid powered vehicle including two driving sources, i.e., the internal combustion engine and an electric motor.
The known hybrid powered vehicle described above includes the internal combustion engine, a generator driven by a driving force of the internal combustion engine, a battery for storing the electric power generated by the electric motor, the electric motor driven by the electric power of the generator or the battery, and a power distributing mechanism for selectively distributing the driving force of the internal combustion engine to the generator and wheels, wherein a start and a stop of the internal combustion engine are controlled corresponding to the driving force required and an electric power accumulation quantity of the battery.
In this type of hybrid powered vehicle, a transmission of the driving force of the internal combustion engine to the generator and the wheels is cut off, or alternatively the internal combustion engine is stopped. Then, the battery electric power is applied to the electric motor, and the wheels are driven by the driving force of the electric motor.
Subsequently, the hybrid powered vehicle is, when in a normal traveling operation, constructed so that the internal combustion engine is actuated, the driving force of the internal combustion engine is distributed to both of the generator and the wheels, then the electric motor is driven by the electric power generated by the generator, and the driving force of the electric motor is transmitted to the wheels. In this case, it follows that the hybrid powered vehicle travels with the driving forces of the internal combustion engine and of the electric motor.
Furthermore, the hybrid powered vehicle is, when in a high-load operation such as an acceleration etc, constructed so that the internal combustion is actuated, the driving force of the internal combustion engine is distributed to the electric motor and the wheels, the electric motor is driven by electric power obtained by adding the electric power generated by the generator to the battery electric power, and the driving force of the electric motor is transmitted to the wheels. In this case, the hybrid powered vehicle travels with the driving forces of the internal combustion engine and of the electric motor as in the case of the normal traveling operation, however, since the battery electric power in addition to the electric power of the generator is applied to the electric motor, the driving force of the electric motor becomes larger than in the normal traveling operation.
Moreover, the hybrid powered vehicle is, when in decelerating and braking operations of the vehicle, constructed so that a transmission of the driving force of the internal combustion engine to the generator and the wheels is cut off, or alternatively the internal combustion engine is stopped, then the electric power regenerated by applying rotary forces of the wheels to the electric motor, and the thus obtained electric power is accumulated in the battery.
Incidentally, the hybrid powered vehicle is, if an electric power accumulated quantity of the battery is under a predetermined value, constructed so that the internal combustion engine is started up, the driving force of the internal combustion engine is distributed to the generator and to the wheels, and the electric power generated by the generator is distributed to the battery and the electric motor, thereby charging the battery with the electric power.
According to the thus constructed hybrid powered vehicle, it is feasible to efficiently operate the internal combustion engine, remarkably reduce a burned fuel rate, decrease a quantity of the exhaust gas and purify the exhaust gas.
By the way, in the hybrid powered vehicle described above, the start and stop of the internal combustion engine are repeated depending on a traveling condition, and hence temperatures of exhaust gas purifying elements such as the exhaust gas purifying catalyst and an air/fuel ratio sensor etc tend to be lower than an activation temperature. If the internal combustion engine is actuated in a state where the temperatures of the exhaust gas purifying elements are lower than the activation temperature, the exhaust gas purifying catalyst is incapable of sufficiently purifying Nox, CO and HC etc in the exhaust gas, resulting in deterioration of the exhaust emission.
What is known as an apparatus for obviating this problem is a control apparatus of an engine driving generator of the hybrid powered vehicle, which is disclosed in Japanese Patent Application Laid-Open Publication No.5-328528. This control apparatus is intended to restrain the deterioration of the exhaust emission, which involves rising an exhaust temperature and an exhaust quantity up to a predetermined quantity by controlling, when the exhaust gas purifying elements such as the exhaust gas purifying catalyst and the air/fuel ratio sensor etc are at low temperatures, an engine output and the number of engine rotations in order to decrease an energy efficiency of the internal combustion engine, and completing a warming-up operation of the exhaust gas purifying elements at an early stage.
The above-described control apparatus of the engine driving generator of the hybrid powered vehicle, even if there is requested a large driving force as needed for the acceleration etc when the warm-up operation of the internal combustion engine is required, preferentially executes the warm-up operation and is therefore incapable of outputting the driving force requested, resulting in such a problem that the drivability declines.